All outboard motors and outdrive units have a downwardly directed fin attached to the lowest extremity of the motor, below a rounded housing which contains a propeller drive shaft, i.e. the lower unit. The fin, which is commonly called a skeg, provides lateral stability and steering capability to the motor, and protection of the propeller from contact with submerged objects.
If the motor lower unit strikes an object, either when the boat is in the water or being trailered, the skeg is usually the first part of the motor to make contact. Ideally, the contact between the skeg and the object will cause the motor to pivot upwardly about an axis significantly above the skeg and propeller, causing the motor to pivot out of harm's way. However, this contact between the skeg and the object frequently causes a portion of the skeg to be broken off or bent. Attempts at repositioning a bent skeg result in breakage of the skeg, which is a casting. Most frequently, only a portion of the skeg is broken off, leaving behind a stub. Skegs are designed to fracture preferentially to prevent more extensive and expensive damage to gears, shafts and bearings which are higher in the motor housing. When the skeg has been broken away from the motor the steering is less sure, the propeller is more vulnerable to fracture, and the torque effect makes steering more difficult.
Conventionally, skeg repairs involve either replacing the entire lower unit or welding a new fin-shaped plate onto the remaining portion of the skeg. When the lower unit is replaced, the operation is expensive (ranging from $400.00 to $1200.00), dependent upon motor size (i.e. H.P.). If a new, typically aluminum, skeg is welded onto the housing, the cost is usually less than replacing the lower unit. Welders willing to work aluminum are few, and those willing require removal, drainage, and disassembly of the lower unit to prevent thermal damage to the nearby seals and bearings. Both conventional repairs are time-consuming, expensive and difficult to accomplish in low population areas where boaters frequently find themselves in need of repairs.
An invention related to the field of boat motor attachments is U.S. Pat. No. 4,995,840 by Seale et al. Seale et al. disclose a fin-shaped attachment which is attached horizontally to a boat motor and is meant to be an extension of the original horizontal appendage. The attachment is intended to enhance the performance of the original boat motor due to its curvature. The curvature of the fin forces the boat motor in the upward direction when a pair of the fin-shaped appendages are attached in their preferred position. Seale et al. do not teach attaching the fin to repair an originally existing appendage, but to enhance the performance of the boat motor.
Zoellner, in U.S. Pat. No. 5,007,869, discloses a device which is attached to the original vertical skeg of a boat motor. Zoellner's device is a vertical sleeve having a horizontal plate attached to its lowest edge. The horizontal plate adds vertical stability to the boat and protection to the propeller. Zoellner's device is attached to a boat motor skeg to prevent damage to the motor and to enhance its performance. In this respect, Zoellner's device is prospective rather than retrospective since its function is to prevent damage to the motor, not to repair the motor after damage. However, since it increases the lowermost dimensions of the motor, it also increases the probability that it will strike a submerged object and cause damage.
Neither Seale et al. nor Zoellner teach a structure for making a repair on a boat motor or replacing an appendage which originally existed but no longer performs as designed. Both of these devices merely affect the original performance of the boat motor, and are intended primarily to increase vertical lift to enhance planing.